Are generators in nested functions possible?

[Chris Liechti]

"Bjorn Pettersen" <BPettersen at NAREX.com> wrote in 
news:mailman.1024614876.11270.python-list at python.org:

> I've got the following code to generate the indicies of all nearest
> neighbours (span levels) in a multi dimensional qube:
> 
> def generateIndexes(length=5, span=1):
>     spanvalues = range(-span, span+1)
>     
>     def genInd(res, length):
>         if length == 1:
>             for val in spanvalues:
>                 yield res + [val]
>         else:
>             for i in range(length):
>                 for val in spanvalues:
>                     genInd(res + [val], length-1)

here you generate generator objetcs and throw them away 'cause you dont use 
them in a loop aor anything!

if you replace that last line with:
    	    	    	    	 for x in genInd(res + [val], length-1):
        	    	    	     	yield x

it yields some data, don't know if it's what you want ;-)


chris





>     return genInd([], length)
> 
> However, when I try to use it it doesn't seem to return anything:
> 
>  >>> for i in generateIndexes(3):
>   ...   print i
>   ...
>  >>>
> 
> I tried getting the iterator (or is it generator?) directly and calling
> next() on it, and it seems like it raises a StopIteration exception
> immediately:
> 
>  >>> g = generateIndexes(3)
>  >>> g.next()
>   Traceback (most recent call last):
>     File "<stdin>", line 1, in ?
>   StopIteration
>  >>>
> 
> Can anyone help me understand what is going on here?
> 
> -- bjorn
> 
> 
> 



-- 
Chris <cliechti at gmx.net>